Machine for processing skins or hides

ABSTRACT

The invention provides a device in a skin treating machine for holding a skin against the knives of a rotating cylinder to enable the latter to perform an accurate skiving operation. It includes a bolster which urges the skin against the knives and extends the full width of the cylinder. The bolster is made of thick rubber, and is supported at several points on a main beam by local screw-operated adjusters. The whole beam is mounted on levers which are hydraulically operated to bring the beam and bolster up to the skin and hold it against the knives. Further automatic adjustment is also provided to accommodate local variations in skin thickness.

Oct. 14, 1975 MACHINE FOR PROCESSING SKINS OR RIDES [75] inventor:Silvio Repetto, Modena, Italy [73] Assignee: S.p.A. Luigi Rizzi & C.,Modena,

Italy [22] Filed: July 18, 1974 [21] Appl. No.: 489,939

[30] Foreign Application Priority Data Aug. 8, 1973 Italy 27652/73 June18, 1974 Italy 24081/74 [52] US. Cl. 69/37 [51] Int. Cl. C148 l/l4 [58]Field of Search 69/37, 42

' [56] References Cited UNITED STATES PATENTS 1.053.297 2/1913 Kehrhahn69/37 2.038.621 4/1936 Whitney 69/37 X 2,638.769 5/1953 Gianoglio 69/422,674.1 14 4/1954 Brill et al. 69/42 3,276,230 10/1966 Horn 69/423,789,632 2/ 1974 Repetto 69/42 FOREIGN PATENTS OR APPLlCATIONS I513.271 11/1930 Germany 69/37 155.348 12/1920 United Kingdom 69/37158,503 6/ 1922 United Kingdom 69/37 Primary Examiner-Alfred R. Guest[57] ABSTRACT The invention provides a device in a skin treating machinefor holding a skin against the knives of a rotating cylinder to enablethe latter to perform an accurate skiving operation. it includes abolster which urges the skin against the knives and extends the fullwidth of the cylinder. The bolster is made of thick rubber, and issupported at several points on a main beam by local screw-operatedadjusters. The whole beam is mounted on levers which are hydraulicallyoperated to bring the beam and bolster up to the skin and hold itagainst the knives. Further automatic adjustment is also provided toaccommodate local variations in skin thickness.

9 Claims, 10 Drawing Figures US. Patent Oct. 14, 195 Sheet 1 of43,911,703

US. Patent Oct. 14, 1975 Sheet 2 of4 3,911,703

Sheet 3 of 4 U.S. Patent Oct. 14, 1975 I MACHINE FOR PROCESSING SKINS ORHIDES PRIOR APPLICATIONS In Italy dated 8th August 1973 and numbered27652 A/73.

In Italy dated 18th June I974 and numbered 24081 A/74.

The present invention concerns a machinefor pro cessing skins or hidesand, in particular, a device for resiliently supporting a skin beingprocessed against the action of the operating tool so as to remove-onlythe surface layer, with the possibility of varying the treatingthickness where necessary and without having to confine treatment toonly one thickness of skin.

As is well known, tanning machines and, in particular, those adapted tothe defleshing of'skins, generally include a tool shaped like anoperating cylinder, rotating in a fixed position, and provided withblades or other types of tools or abrasive surfaces, and conveyorrollers for feeding the skins.

The conveying rollers are motor-driven and comprise a rubber-coveredcylinder over which the skin is extended, and two feeding rollers ofsteel with knurled surfaces, which press the skin against therubbercovered cylinder, thus effecting the feed movement thereof.

The bladed cylinder for removing the flesh from the inner side of theskin, works against a resilient bolster forming part of the supportdevice which, in conventional machines, is a solid or hollow rubbercylinder, mounted on a beam parallel to the bladed cylinder and lockedbetween upper and lower jaws which leave only a small arc exposed whichcomes into contact with the skin.

The rubber cylinder is urged against the skin to a predeterminedposition based on the average thickness of the skin itself; however, inview of the considerable local differences in the thickness ofa skin,such as cowhide, the elasticity of the rubber cylinder is not sufficientto absorb the variations in thickness, for which purpose the lower jawis generally divided into sectors, each of which is separatelyadjustable and subjected to the action of resilient means.

This known device for supporting the skin has many disadvantages, thefirst of which is possible damage to the outer surface caused byaccidental contact with the bladed cylinder. In this case it isnecessary to vary the position of the rubber cylinder between the metaljaws in order to place an integral portion of the cylinder itself incontact with the skin being processed, this operation being possibleonly for a limited number of times both for the variation in diameterwhich the rubber cylinder assumes and for the differential engagementbetween the metal jaws, due to variation in shape, with consequentinsufficiency of projection of the support cylinder towards the jawsthemselves.

If the support cylinder is hollow and kept under pressure by compressedair, the disadvantage of accidental contact with the bladed cylinder iseven greater on account of the possible bursting of the support cylinderresulting from superficial damage.

A second series of disadvantages inherent in known devices is due to themeans for controlling and spring mounting the various parts which haveto be used.

These disadvantages reside substantially in the possibility of the meansbecoming locked on account of inerustations and corrosions forming as aresult of the presence of the chemical substances with which the skinsare washed in the course of processing.

These serious disadvantages are eliminated by the skin supporting deviceof the present invention, which involves no loss of time in replacementor rotation of the support bearing and eliminates the need to usepneumatic means for supplying the required elasticity thereof.

According to the present invention there is provided a device in a skintreating machine for the resilient support ofa skin having variations inthickness, comprising a beam displaceable relatively to an operatingcylinder, on which beam there is mounted on plane guides a resilientbolster transversely adjustable by adjusting units located at regularspaced intervals over the entire length of the bolster so as to causethe bolster to assume a transverse line best adapted to the thickness ofthe skin being processed, and hydraulic means for setting the basictreatment thickness and for increasing this thickness in accordance withthe dimensions of the skin. 1 I

The elastic bolster has a substantially parallelopiped shape, and mayhave reduced portions, longitudinal outlets or grooves for the purposeof increasing its elasticity in a transverse direction, and ispreferably provided in the rear portion with a flexible metalstrippermitting connection with the position adjusting units.

According to one embodiment, the elastic rubber bolster may have one ormore series of vertical, cylindrical, transverse holes distributed overits length and towards the rear end of the bolster. The holes may beprovided with longitudinal outlets or channels both in theparallelopiped bolster of a single material, and in combination with thereduced portions, and also in combination with layers of differentelasticity.

The vertical holes may be distributed uniformly over the entire lengthof the bolster or grouped in predetermined areas of the bearing, ordistributed variously over the length, particularly where the horizontalthrust is applied by the means adjusting the position and the distance.

Said vertical holes have the purpose of permitting variation in thetransverse elasticity of the bolster, both in relation to theirdimensions and their distribution, and plugs of more or less elastic orrigid material maybe introduced into all or some of the holes, thuspermitting further variation in the elasticity of the bolstercorresponding to zones of the skin being processed, in which there arenormally appreciable variations in thickness.

The plugs may partially or completely fill one or more holes. The holesthemselves may also have shapes differing from the cylindrical, and maybe elongated or elliptical.

The position adjusting units are formed by means capable of transverselydisplacing the elastic bolster, and may comprise externally controlledmale and female screw means for locking in position, or by hydraulicmeans for obtaining small displacements and representing a fixed supportpoint for the rear part of said parallelopiped elastic bolster.

The elastic support device comprises, as stated, a beam which istransversely displaceable and the movement of which is determined byhydraulic means interposed at the ends between the cross-piece and theopening and closing levers of the machine; the means may include pistonand cylinder units controlled by.

valves which are in turn adjusted by screw means actuated by a handwheel for adjusting the thickness of the skin. Alternatively, thethickness may be varied, by means of the hydraulic units, relatively tothe thickness of the skin, the requirements of the processing and/or thewear on the blades and/or on the bolster, by control means operating thehydraulic valves which control the positioning units located at the endsof the beam.

With the device of the present invention, in addition to eliminating thedisadvantages of solid or hollow rubber cylinders having a pneumaticaction, it is possible to obtain both faster and more precise processingdue to the resilient bolster, which does not require replacementoradjustments, and which provide more economical processing since thecontrol means are not subjected to incrustations and corrosions, onlythe elastic parallelopiped being exposed, this is slidable between theplane guides of the beam, whilst the rear control units are completelyprotected and hermetically sealed.

These and other features will become apparent from the followingdetailed description of an embodiment of a skin supporting deviceaccording to the present invention, illustrated in the accompanyingdrawings, in which:

FIG. 1 shows a front view of a defleshing machine including the device;

FIG. 2 shows a cross-section through the machine, taken on line IIII ofFIG. 1;

FIG. 3 shows on a magnified scale the details of the central part of thesection taken on line II-II;

FIG. 4 shows a perspective view of the machine;

FIGS. 5 9 show various embodiments of the elastic bolster incross-section; and

FIG. shows an elastic bolster with a plurality of holes, located in theworking position relatively to the bladed cylinder in the defleshingmachine.

FIGS. 1 and 2 show the defleshing machine as a whole. It comprises twosides 2, 3 connected at the bottom by a base 1 and at the top by a beam4, in which framework a bladed cylinder 5 is mounted and driven torotate by a suitable motor.

Supported on the sides 2, 3 are two levers 6, 7 pivoted at 8; they arecontrolled by connecting rods 9 and cam 10 so as to be movable along anarcuate slot 11. At the upper end, each lever supports a driven roller12 with a rubbercovered surface for supporting a skin during processing.

A second pair of levers l3, pivoted on the beam 4, supports a drivenconveyor roller 14 and is urged to bring roller 14 into contact withroller 12 by pressure cylinders 15. Another pair of levers l6 pivoted onbeam 4, supports a second driven conveyor roller 17 and is urged tobring roller 17 into contact with roller 12 by pressure cylinders 18.

A beam 19, extending between the two levers 6, 7, is displaceablehorizontally on brackets 20, 21 (FIGS. 1 and 4) connected to the levers6, 7 by hydraulic pistons 22a, 22b, 23a 23b and held in a stableposition by valves 34, 35 the slides 34a, 35a of which are adjusted bymeans of gear units 24, 25 connected together by a shaft 26 rotated by ahand wheel 40. The units 24, 25 are connected to the levers 6 and 7 andto the slides 34a, 35a.

On the upper part of the displaceable beam 19 there are plane parallelguides 27, between which there is interposed a resilient bolster 28 ofrubber or like substance, having a substantially parallelopiped shapeand capable of sliding between the guides 27. The resilient bolster 28is connected to a flexible metal belt 29 at its rear end and thusconnected to a plurality of uniformly spaced control units along thebeam 19, each comprising a threaded shaft 30 which screws on a bush 3]and is externally rotatable by a hexagon end 32. The.interior of eachcontrol unit is sealed by suitable seals and known means are providedfor preventing unscrewing of the bush.

The resilient bolster 28 projects from the guides 27 towards bladedcylinder 5 and is located, with the machine closed, radially relativelyto the bladed cylinder.

The cross-section of the resilient bolster may be seen in FIG. 5; it maybe divided into more than one part and extends the entire length of thebladed cylinder 5.

The composition of the bolster 28 must allow sufficient elasticity forabsorbing normal variations in the thickness of the skin being processedand, for this purpose, it is possible to shape it with a rear reducedportion, as shown in FIG. 6, and also to construct the block in twoparts 28a and 28b using materials of different hardness and elasticityso as to increase the total elasticity of the bolster itself in thedirection of the thrust, which is in the direction of the arrow Z.

According to the variant shown in FIG. 7, vertical transverse holes 50are provided in the bolster 28, in the rear part thereof, the holeshaving dimensions, shapes and distribution so as to permit anappreciable variation of elasticity in the direction of the thrust ofthe skin being processed, i.e. horizontally, as shown by the arrow Z.

With reference to the embodiment shown in FIG. 8, the bolster is formedin two parts 28a 28b with materials having different hardness andelasticity. In one of the parts 28b, a longitudinal groove 28c isformed, with a plurality of vertical transverse holes 50 distributedlongitudinally. The holes may have different diameters and shapes, andmay be disposed in different positions.

The longitudinal distribution of the holes 50 in the bolster 28 may beeffected in any order, either with uniform spacing, or grouped inspecific zones of the bolster, as shown in FIG. 10, the zonescorresponding with each other and coinciding with control units on whichthe rear end of the bolster is supported, each control unit beingadjusted by its hexagon end 32. The presence of the holes 50 permitsgreater elasticity of the bolster 28 near the rear supports in order toequalise the elasticity of the bolster 28 and the associated metal strip29 in the spaces between one of the supports and the next. In each casethe elasticity of the bolster may be subsequently varied as desired; forexample, the bolster with the plurality of holes may have plugs 51introduced into some or all of the holes, as shown in FIG. 9, the plugsbeing made of any suitable elastic or rigid material, and playing a partboth in longitudinal distribution and in elasticity or hardness, in thetotal elasticity of the bolster.

The above-described resilient support device, composed of the beam 19and the resilient bolster 28, is provided with hydraulic means forvarying the position of the end of the bolster 28 relatively to theperiphery of the bladed cylinder 5.

The object of this means is to effect the adjustment of the basicthickness, i.e. the space which must exist during processing, betweenthe support bearing 28 and the bladed cylinder 5, as a function of thethickness of the skin to be processed.

These means comprise two hydraulic units connected to the ends of thebeam 19 for positioning it relatively to the levers 6 and 7 andcomprising the pistons 22a, 22b and 23a, 23b, the valves 34, 35 withrespective slides 34a, 35a controlled by the units 24, 25, and thecylinders 34b, 35b. Each cylinder 34b, 35b is provided in its centrewith an inlet P for pressurised fluid, and two discharge outlets Slocated at the end.

By rotating the hand wheel 40 in a clockwise direction, it is possibleto advance the slides 34a, 35b towards the interior of the machine(direction C, FIG. 4). In this manner the pressure from inlet P isapplied to pistons 22a, 23a and pressure on pistons 22b, 23b, isrelieved through discharge outlets S causing the advance of the beam 19in the direction C (closing direction) by the same amount as the slides34a and 35a are displaced. The advancing beam 19 drives with it thecylinders 34b and 35b of the valves 34 and 35 until the slides 34a and35a, which are not displaced, close the communicating bores between thepistons 22a, 22b and 23a, 23b and the cylinders 34b and 35b.

Conversely, by rotating the hand wheel 40 in an anticlock-wisedirection, the displacement of the beam 19 is effected in the directionD (opening direction).

During some phases in the processing of a skin, it is advisable to beable to make variations in thickness, i.e., to vary the position of thebolster 28 in a direction which increases the space between its frontedge and the bladed cylinder 5 by a set amount.

This is particularly useful at the time of the closing of the machine toprevent the skin being suddenly squeezed between the bolster 28 and thebladed cylinder 5 before the conveyor rollers 14 and 17 effect a feed,thus avoiding initial contact marks of the blades on the stationaryskin. Secondly, it is necessary to increase the space between thebolster 28 and the bladed cylinder 5 when a portion of skin passesbetween them having a thickness greater than that which is normallycompensated by the elasticity of the bolster 28, for example, in thearea of the neck or head of the skin, the thickness of which may be twoor three times greater than the average thickness of the remaining partof the skin. This considerable increase in local thickness cannot becompletely absorbed by the elastic bolster and on previous machines thisresults in the stopping of the skin with consequent slippage between theconveyor rollers, or the lateral displacement of the skin caused by thethrust of the spiral blades. In each case, the operator is obliged toopen the machine and set a new thickness adjustment.

The means provided for such variation in thickness during the processingof a skin consists of a hydraulic unit indicated generally by 33(FIG. 4)which acts on the cylinders 34b, 35b of valves 34, 35 by means of theshafts 36, 37 having at their ends oblique slots 38, 39 which arecoupled to valve cylinders 34b, 35b to control the pressure on pistons22a, 22b and 23a, 23b for the transverse displacement of the beam 19carrying the bolster, using the hydraulic system already described foradjusting the basic thickness. For this purpose, the cylinders 34b, 35bof the valves 34, 35 are displaced by the displacement of slots 38, 39to which the valve cylinders are coupled by yokes affixed to thecylinders and moving in the slots. This unit 33 includes two co-axialhydraulic pistons, the outer one 41 of which has different opposedsurfaces and forms the cylindcr of the inner one 42. i

The latter is connected to the shafts 36, 37 provided at the ends withoblique slots 38, 39 acting directly on the cylinders 34b, 35b of thevalves 34, 35. The inner piston 42 is actuated through an electricallyoperated valve (not shown) by pressurised fluid supplied to the inlet Pand discharging through the outlet S. The inner piston 42 is normallyurged towards the right under the action of the pressure P, but may bemoved to the left under the control of the operator at any moment duringthe operating phase, thus causing a movement to the left (arrow E) ofthe rods 36, 37 and associated oblique slots 38, 39.

The movements of the inner piston 42 may be limited in the direction ofthe arrow E by an adjustable mechanical stop 49 and locked on the shaft37 by the screw 49a.

The outer piston 41 is connected hydraulically in the opening andclosing phases of the machine through the openings M and P, as will besubsequently described. The control of the levers 6 and 7 pivoted on theshaft 8, by way of the connecting rod 9 and handle 10, is obtained byrotation of the shaft 44a by the pinion 44 engaging on the rack of thepiston 43 and displaceable in the cylinder 45. The cylinder receivespressurised fluid from the lower opening P to effect rising movement ofthe piston 43 (Arrow A and from the upper opening M for movement thereofdownwardly (arrow 8,). Before the end of the downward movement, thepiston 43 exposes an outlet m for the pressure fluid so as to controlthe positioning members for the closure of the machine.

The operation of the machine is as follows:

Firstly, it is necessary to arrange the projecting profile of thebolster 28 by turning polygonal heads 32 to move threaded sleeves 31until the profile itself is adapted to the variations in thickness ofthe skin in a transverse direction. The basic thickness is thenestablished by rotating the hand wheel 40 so as to regulate the averagespace between the projecting edge of the bolster 28 and the bladedcylinder 5 according to the thickness of the skin to be processed.

At this point bolster 28 has been adjusted to the characteristics of theskin being processed, and the machine is ready to execute the openingphase and the closing phase in order then to carry out the actualprocessing. In order to bring the installation to the machine openphase, pressurised fluid from a suitable hydraulic system (not shown)enters the cylinder 45 from inlet P whereby the piston 43 is urgedupwardly (arrow A causing the gear 44 and the associated shaft 44a torotate in the direction of the arrow A and consequently to pivot camsl0, connecting rods 9 and levers 6, 7 in the direction A A and Aremoving the roller 12 from the bladed cylinder 5.

The pressurised fluid is also fed to actuate the piston 41, through theopening P in the cylinder 33, whereby the cylinder is urged to the left,taking with it the piston 42 which, in its normal position, is urged tothe right by its own independent circuit, urging to the left shafts 36,37 in the direction of arrow E.

This movement causes the advance of the cylinders 34b, 35b of the valves34, 35 in the direction of the arrow C, with consequent opening of thepassage between inlet P of the pressure fluid and the conduit whichleads to the pistons 22b, 23b, to apply pressure fluid to the pistonswhich, bearing against the levers 6, 7 cause the beam 19 to open (in thedirection of the arrow D). This displacement stops when slides 34a, 35aclose the communicating bores between pistons 22a, 22b and 23a, 23b andcylinders 34b, 35b, which are displaced in the direction of the arrow D,since they are connected to the beam 19. The driving roller 12 is in theopen position, i.e. at the bottom of the opening movement indicated byarrow A (FIG. 2).

At this point the operator can position the skin on the roller 12 andstart the machine in the closing phase. In this phase pressure fluid isfed through port M of the cylinder 45 urging the rack piston 43downwardly (arrow B,). This movement causes rotation of the pinion 44and hence of the shaft 44a in the direction pivoting of arrow B, andconsequently of the cam 10, connecting rod 9 and lever 7 (similarly onthe other side of the lever 6) in the direction of the arrows B B Buntil the end of the closing movement indicated by arrow B in FIG. 2. Atthis point the roller 12, with the associated skin, is in contact withrollers l4, 17. The resilient bolster 28 is disposed in front of thebladed cylinder 5 but its spacing therefrom is determined by theadjustment of the basic thickness with an increment due to the featurethat piston 41 is again displaced to the left (arrow E), with theconsequence that, as stated, the beam 19 is displaced in an openingdirection (arrow D).

At the moment piston 43 completes its downward movement (arrow 8,), ituncovers the opening M of cylinder 45 and the pressurized fluid, comingfrom M, is fed to (a) hydraulic units 18 (FIGS. 1 and 2) which, by meansof levers l3 and 16, urge rollers l4, 17 against roller 12; (b) to ahydraulic motor (not shown) which, by way of transmissions 46, 47, 48(FIG. 4) rotates rollers 12, 14, 17,. starting the feed of the skins;and (c) to opening M of cylinder 33, pressing on differential piston 41which, having a surface greater than that which is turned towardsopening P at the side of opening M, is urged to the right (arrow F),followed by the piston 42 which is constantly fed from inlet P. In thismanner, rods 36, 37 and oblique slots 38, 39 are displaced to the right(arrow F). This movement causes the advance of cylinders 34b35b in thedirection of arrow D, with the consequence that the beam 19 is displacedin the direction of arrow C, until reestablishment of the hydraulicbalance is obtained by the closing of the openings by the slides 34a,35a.

Consequently, with the closing of the machine, the beam 19 is in a moreretracted position relatively to that established by the adjustment ofthe basic thickness. Only after the rollers 12, 14, 17 have been startedand hence the skin advanced and at the end of the travel of the pistons41 and 42 is the distance between the outer edge of the bolster 28 andthe bladed cylinder 5 predetermined by operating the hand wheel 40. Inthis manner, a pressure mark of the blades on the skin is avoided.

During the processing, the bladed cylinder 5 cuts the flesh from theinside of the skin while the skin is carried upwardly. Any elevations orcavities existing in the skin surface are absorbed by the resilientbearing 28.

When the operator considers it advisable, he can feed pressurised fluidthrough port S to the piston 42 by means of a valve, displacing it fromthe right, where it had been, to the left in the direction of the arrowE, with consequent movement of the rods 36, 37 and withdrawal of thebeam 19, thus increasing the space between the bearing 28 and the bladedcylinder 5.

The amount of this increase may be set by suitably positioning the stop49 on the rod 37.

When processing is concluded, the operator reverses the flow of fluid,causing it to reach the cylinder 45 via opening B in order to urge thepiston 43 upwardly and terminate the already described openingoperations.

I claim: I. A device in a skin working machine for the resilient supportof a skin having an average thickness and variations in the thickness,which machine comprises a framework, a skin working cylinder mounted onthe framework, a beam mounted on the framework for displacement relativeto the skin working cylinder and plane guide means on the beam, and theresilient support including a resilient bolster mounted on the planeguide means for reciprocation in the plane guide means towards and awayfrom the working cylinder, the bolster having a substantiallyparallelopiped shape and defining longitudinal grooves extending in thedirection of the beam and a plurality of transverse bores substantiallyperpendicular to the grooves near an end of the bolster remote from theskin working cylinder, an opposite end of the bolster adjacent the skinworking cylinder forming a nip therewith for receiving the skin, aplurality of adjusting units spaced regularly along the entire length ofthe bolster in said direction and arranged to adjust the spacing of theopposite bolster end from the working cylinder in accordance with theaverage thickness of the skin being worked, and hydraulic means fordisplacing the beam relative to the working cylinder whereby the nip isset to a basic thickness corresponding to the average thickness of theskin being worked, and for further displacing the beam whereby the nipis set to an operating thickness corresponding to variations in theaverage skin thickness.

2. A device in a skin working machine as defined in claim 1, wherein thetransverse bores are irregularly spaced along the bolster in saiddirection, the bores having different diameters and shapes.

3. A device in a skin working machine as defined in claim 1, wherein thetransverse bores are grouped, groups of the bores being aligned withrespective ones of the adjusting units.

4. A device in a skin working machine as defined in claim 1, furthercomprising plugs of elastic material inserted in at least some of thetransverse bores.

5. A device in a skin working machine for the resilient support of askin having an average thickness and variations in the thickness, whichmachine comprises a framework, a skin working cylinder mounted on theframework, a beam mounted on the framework for displacement relative tothe skin working cylinder and plane guide means on the beam, and theresilient support including a resilient bolster mounted on the planeguide means for reciprocation in the plane guide means towards and awayfrom the working cylinder, the bolster having an end remote from theworking cylinder, and an opposite end forming a nip therewith forreceiving the skin, a plurality of adjusting units spaced regularlyalong the entire length of the bolster in the direction of the beam andarranged to adjust the spacing of the opposite bolster end from theworking cylinder in accordance with the average thickness of the skinbeing worked, and hydraulic means for displacing the beam relative tothe working cylinder whereby the nip is set to a basic thicknesscorresponding to the average thickness of the skin being worked, andforfurther displacing the beam whereby the nip is set to an operatingthickness corresponding to variations in the average skin thickness, thehydraulic units having oppositely disposed pistons for displacing thebeam, and displaceable slide valves controlling the pistons of thehydraulic units, a first slide valve being manually controllable formoving a respective one of thehydraulic units for setting the nip to thebasic thickness, and a second slide valve being automatically controlledin response to variations in the skin thickness for setting the nip tothe operating thickness.

6. A device in a skin working machine as defined in claim 5, furthercomprising a pair of pivotal levers sup-,

porting the beam ends displaceably relative to the skin workingcylinder, the hydraulic units each comprising a cylinder housingrespective one of the pistons, the pistons being connected to the leversfor movement therewith, and the cylinders being connected to the beamand being controlled for movement by the second slide valves.

7. A device in a skin working machine as defined in claim 6, wherein thesecond slide valve comprises two coaxial hydraulic pistons, an externalone of the two pistons forming a cylinder for the internal piston, andfurther comprising mechanical means controlled and operated by theinternal piston, the mechanical means being arranged to control and movethe cylinders of the hydraulic units.

8. A device in a skin working machine for the resilient support of askin having an average thickness and variations in the thickness, whichmachine comprises a framework, a skin working cylinder mounted on theframework, a beam extending in a longitudinal direction, a pair ofpivotal levers supporting the beam ends on the framework fordisplacement of the beam relatively to the skin working cylinder formoving the beam between an open and a closed position in relation to theworking cylinder, the beam ends being horizontally displaceably mountedon the levers, plane guide means on the beam, and the resilient supportincluding a resilient bolster mounted on the plane guide means forreciprocation in the plane guide means towards and away from the skinworking cylinder, the bolster having an end remote from the workingcylinder and an opposite end forming a nip therewith for receiving theskin, a plurality of adjusting units spaced regularly along the entirelength of the bolster in said direction and arranged to adjust thespacing of the opposite bolster end from the working cylinder inaccordance with the average thickness of the skin being worked, eachbeam end defining a pair of oppositely directed hydraulic cylindersextending transversely to said direction, a pair of pistons connected toeach lever and extending into a respective ones of the cylinders, afirst slide valve including a cylinder part and a piston part slidablein respect of each other for controlling flow of hydraulic fluid intothe cylinders of each beam end, one of the slide valve parts beingmanually controllable for horizontally displacing the beam relative tothe working cylinder whereby the nip is set to a basic thicknesscorresponding to the average thickness of the skin being worked, and asecond slide valve automatically controlled in response to variations inthe skin thickness when the beam is in the closed position and operatingthe other slide valve part for further displacing the beam relative tothe working cylinder whereby the nip is set to an operating thicknesscorresponding to variations in the average skin thickness.

9. A device in a skin working machine for the resilient support of askin as defined in claim 8, wherein the second slide valve comprises twocoaxailly hydraulic pistons, an external one of the two pistons of thesecond slide valve forming a cylinder for the internal piston thereof,and further comprising mechanical means controlled and operated by theinternal piston, the mechanical means being arranged to move the otherslide valve part of the first slide valve.

1. A device in a skin working machine for the resilient support of askin having an average thickness and variations in the thickness, whichmachine comprises a framework, a skin working cylinder mounted on theframework, a beam mounted on the framework for displacement relative tothe skin working cylinder and plane guide means on the beam, and theresilient support including a resilient bolster mounted on the planeguide means for reciprocation in the plane guide means towards and awayfrom the working cylinder, the bolster having a substantiallyparallelopiped shape and defining longitudinal grooves extending in thedirection of the beam and a plurality of transverse bores substantiallyperpendicular to the grooves near an end of the bolster remote from theskin working cylinder, an opposite end of the bolster adjacent the skinworking cylinder forming a nip therewith for receiving the skin, aplurality of adjusting units spaced regularly along the entire length ofthe bolster in said direction and arranged to adjust the spacing of theopposite bolster end from the working cylinder in accordance with theaverage thickness of the skin being worked, and hydraulic means fordisplacing the beam relative to the working cylinder whereby the nip isset to a basic thickness corresponding to the average thickness of theskin being worked, and for further displacing the beam whereby the nipis set to an operating thickness corresponding to variations in theaverage skin thickness.
 2. A device in a skin working machine as definedin claim 1, wherein the transverse bores are irregularly spaced alongthe bolster in said direction, the bores having different diameters andshapes.
 3. A device in a skin wOrking machine as defined in claim 1,wherein the transverse bores are grouped, groups of the bores beingaligned with respective ones of the adjusting units.
 4. A device in askin working machine as defined in claim 1, further comprising plugs ofelastic material inserted in at least some of the transverse bores.
 5. Adevice in a skin working machine for the resilient support of a skinhaving an average thickness and variations in the thickness, whichmachine comprises a framework, a skin working cylinder mounted on theframework, a beam mounted on the framework for displacement relative tothe skin working cylinder and plane guide means on the beam, and theresilient support including a resilient bolster mounted on the planeguide means for reciprocation in the plane guide means towards and awayfrom the working cylinder, the bolster having an end remote from theworking cylinder, and an opposite end forming a nip therewith forreceiving the skin, a plurality of adjusting units spaced regularlyalong the entire length of the bolster in the direction of the beam andarranged to adjust the spacing of the opposite bolster end from theworking cylinder in accordance with the average thickness of the skinbeing worked, and hydraulic means for displacing the beam relative tothe working cylinder whereby the nip is set to a basic thicknesscorresponding to the average thickness of the skin being worked, and forfurther displacing the beam whereby the nip is set to an operatingthickness corresponding to variations in the average skin thickness, thehydraulic units having oppositely disposed pistons for displacing thebeam, and displaceable slide valves controlling the pistons of thehydraulic units, a first slide valve being manually controllable formoving a respective one of the hydraulic units for setting the nip tothe basic thickness, and a second slide valve being automaticallycontrolled in response to variations in the skin thickness for settingthe nip to the operating thickness.
 6. A device in a skin workingmachine as defined in claim 5, further comprising a pair of pivotallevers supporting the beam ends displaceably relative to the skinworking cylinder, the hydraulic units each comprising a cylinder housingrespective one of the pistons, the pistons being connected to the leversfor movement therewith, and the cylinders being connected to the beamand being controlled for movement by the second slide valves.
 7. Adevice in a skin working machine as defined in claim 6, wherein thesecond slide valve comprises two coaxial hydraulic pistons, an externalone of the two pistons forming a cylinder for the internal piston, andfurther comprising mechanical means controlled and operated by theinternal piston, the mechanical means being arranged to control and movethe cylinders of the hydraulic units.
 8. A device in a skin workingmachine for the resilient support of a skin having an average thicknessand variations in the thickness, which machine comprises a framework, askin working cylinder mounted on the framework, a beam extending in alongitudinal direction, a pair of pivotal levers supporting the beamends on the framework for displacement of the beam relatively to theskin working cylinder for moving the beam between an open and a closedposition in relation to the working cylinder, the beam ends beinghorizontally displaceably mounted on the levers, plane guide means onthe beam, and the resilient support including a resilient bolstermounted on the plane guide means for reciprocation in the plane guidemeans towards and away from the skin working cylinder, the bolsterhaving an end remote from the working cylinder and an opposite endforming a nip therewith for receiving the skin, a plurality of adjustingunits spaced regularly along the entire length of the bolster in saiddirection and arranged to adjust the spacing of the opposite bolster endfrom the working cylinder in accordance with the average thickness ofthe skin being worked, each beam end defiNing a pair of oppositelydirected hydraulic cylinders extending transversely to said direction, apair of pistons connected to each lever and extending into a respectiveones of the cylinders, a first slide valve including a cylinder part anda piston part slidable in respect of each other for controlling flow ofhydraulic fluid into the cylinders of each beam end, one of the slidevalve parts being manually controllable for horizontally displacing thebeam relative to the working cylinder whereby the nip is set to a basicthickness corresponding to the average thickness of the skin beingworked, and a second slide valve automatically controlled in response tovariations in the skin thickness when the beam is in the closed positionand operating the other slide valve part for further displacing the beamrelative to the working cylinder whereby the nip is set to an operatingthickness corresponding to variations in the average skin thickness. 9.A device in a skin working machine for the resilient support of a skinas defined in claim 8, wherein the second slide valve comprises twocoaxailly hydraulic pistons, an external one of the two pistons of thesecond slide valve forming a cylinder for the internal piston thereof,and further comprising mechanical means controlled and operated by theinternal piston, the mechanical means being arranged to move the otherslide valve part of the first slide valve.